This invention relates to corner joint used at the four corners of a chassis of a handcart, a shelf-frame cart, a box cart or a flat cart, to a chassis assembled using said corner joint, and to a cart assembled using said chassis.
Known corner joints and chassis assembled using them, such as those described in Japanese Published Patent Application No. 12608/1991, are formed as products of injection molding from synthetic resin or from worked metal, and are rectangular in shape seen in a plan view. Along the rectangular outer periphery, two rising parts of inverted U shape are provided and insertion grooves are formed therein to receive flanges or angled webs that serve as longitudinal or transverse frames of a chassis. A number of attachment holes are provided in the longitudinal direction along the rising parts, and rectangular bolt holes are used for attaching universal wheels and fixed wheels to a support plate that connects the rising parts. A chassis that can be modified in plan shape and size is easily constructed by attaching universal wheels or fixed wheels to said support plate, inserting the flanges or angled webs, having a number of spaced attachment holes formed in the longitudinal direction, into said two grooves for forming a right angle therebetween, and by inserting bolts into selected attachment holes of the angled webs through the attachment holes of the rising parts which are aligned thereto. A cart is completed by mounting an upper structure thereon, such as a framework or a handle set for hand pushing.
The known corner joint described above, however, is constructed by using angled webs for frame members, and therefore cannot be employed well under erosive conditions, for example, in the presence of seawater and agricultural chemicals, because the angled webs are made of steel, are heavy and are easily rusted. Further the known chassis are not practical in that they do not have the means to mount an upper structure of a cart thereto and are especially lacking in a means to facilitate repair, modification, and replacement of the upper structure of the cart.